Thiocarbonates

ABSTRACT

Thiolcarbonates represented by the formula,   The thiolcarbonates can be easily produced by reacting an alkali metal salt of 2-mercaptopyrimidine with phosgene, and reacting the resulting thiolchloroformate with an alcohol (R3OH), or by reacting a 2-mercaptopyrimidine with a halo-carbonic acid ester.   WHEREIN R1 and R2 are individually a hydrogen atom or a methyl group, and R3 is a straight chain or branched chain saturated or unsaturated alkyl group having 1 to 5 carbon atoms or is a benzyl or benzhydryl group which may be nuclear substituted, are quite useful for protecting the amino or imino groups of amines, hydrazines, amino acids and peptides with groups of the formula   D R A W I N G

' United States Patent 1191 Nagasawa et al.

[ Dec. 3, 1974 1 1 THIOCARBONATES [73] Assignee: Nitto Boseki Co. Ltd., Fukushima-shi, Japan [22] Filed: Sept. 8, 1972 [21] Appl. No.: 287,410

[31)] I Foreign Application Priority Data Sept. 17, 1971 Japan 46-72261 Sept. 27, 1971 Japan 46-75306 Sept. 30, 1971 Japan 46-76555 Jan. 10, 1972 Japan., 47-5116 [52] US. Cl. 260/251 R, 260/471 C, 260/482 C,

OTHER PUBLICATIONS Kinugawa et 211., Yakugaku Zasshi 80, 1559-l564, (1960). Weitzel et al., HoppeSeylers, Z. Physiol. Chem, 346(2), 208-223, (1966).

Primary ExaminerG. Thomas Todd Attorney, Agent, or Firm-Karl W. Flocks [5 7] ABSTRACT Thiolcarbonates represented by the formula,

N If

-s -0 o R N wherein R and R are individually a hydrogen atom or a methyl group, and R is a straight chain or branched chain saturated or unsaturated alkyl group having 1 to 5 carbon atoms or is a benzyl or benzhydryl group which may be nuclear substituted, are quite useful for protecting the amino or imino groups of amines, hydrazines, amino acids and peptides with groups of the formula C O R The thiolcarbonates can be easily produced by reacting an alkali metal salt of Z-mercaptopyrimidine with phosgene, and reacting the resulting thiolchloroformate with an alcohol (R 011), or by reacting a 2- mercaptopyrimidine with a halo-carbonic acid ester.

11 Claims, 22 Drawing Figures mmmm: 31m

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/ TRANSMISSION WAVE NUMBER (cm') THllOCARBONATlES This invention relates to novel thiolcarbonates, a pro cess for producing the same and a process for application thereof.

Amines and hydrazines having protected amino and- /or protected peptides, are quite useful compounds as starting materials for synthesis of various peptides which are extremely useful as foods and pharmaceuticals, or for synthesis of other compounds.

Recently, it has come to be widely recognized that in the synthesis of N-protected amino acids and N- protected peptides, t-alkyloxycarbonyl groups such as t-butyloxycarbonyl and t-amyloxycarbonyl groups; benzhydoxycarbonyl groups; and nuclear substituted or unsubstituted benzyloxycarbonyl groups such as benzyloxycarbonyl, p-methoxybenzyloxycarbonyl, p-nitrobenzyloxycarbonyl, p-chlorobenzyloxycarbonyl and p-bromobenzyloxycarbonyl groups are useful as protective groups for amino and/or imino groups of amines and hydrazines, particularly amino acids and peptides. Among these protective groups, the talkyloxycarbonyl groups are easily cut from the protected amino or imino groups by means of acids but are stable to catalytic reduction, whereas the benzyloxycarbonyl group is stable to acids but is easily cut by catalytic reduction. Taking advantage of such differ ences in stability between protective groups, the synthesis of complex peptides has extensively been conducted selectively. Further, a peptide synthesis method called solid-phase method has recently been developed by R. B. Merrifield [Journal of American Chemical Society, 85, 2149 (1963)]. Amino acids, which have the above-mentioned t-alkyloxycarbonyl groups or nuclear substituted or unsubstituted benzyloxycarbonyl groups as protective groups, have come to be used also as starting components in said solid-phase method, and the importance thereof has come increasingly greater.

As acylating agents for preparation of such N- protected amines and hydrazines, various compounds have heretofore been proposed. For example, t-alkyl p-nitrophenyl carbonates [Journal of American Chemical Society, 79, 6180 (1957); Chemische Berichte 95, 1 (1962)], t-alkyl N-hydroxysuccinimidyl carbonates [Tetrahydron Letters, 39, 4765 (1966)], t-alkyl 8- hydroxyquinolyl carbonate [Liebigs Annalen der Chemie, 716, 216 (1968)], t-alkyl 2,4,5-trichlorophenyl carbonates [Journal of Chemical Society (C), 2632 (1967)]; Liebigs Annalen der Chemie, 724, 204 1969)], t-alkyl pentachlorophenyl carbonates [Japanese Patent Publication Nos. 19,685/70 and 36,729/70],

t-alkyloxycarbonyl azides [Journal of American Chernical Society, 79, 442 1957 s 1,95511959) ,82, 2725 (1960); Bulletin ot'the'Ch'eriii'cal Society of Japan, 37,

204 (1969)] have been known as aralkyloxycarbonylating agents.

However, the above-mentioned known alkyloxycarbonylating agents and aralkyloxycarbonylating agents (hereinafter, these are inclusively referred to as acylating agents) have many such drawbacks as mentioned below.

Starting materials for synthesis of the acylating agents are expensive; operations for synthesis thereof are complex and require a long period of time, a high temperature and the like severe conditions; and the resulting acylating agents themselves are unstable. Operations for acylating amines and hydrazines by use of the above-mentioned acylating agents are complex, require a long period of time, a high temperature and the like severe conditions; the conversion of acylation is low; the acylating agents have such selectivity as to react with only specific amines and hydrazines; the acylation products are difficultly purified; and, in case amines and hydrazines to be acylated have other active groups in addition to amino and/or imino groups, the said other groups should have previously been protected. Despite the fact that in such acylation, particularly in the acylation of amino acids and peptides, the purification of acylation products is an extremely important question, the above-mentioned known acylating agents, particularly mixed carbonates of phenols, have such great drawback that phenols, which are released with progress of the reaction, tend to migrate in the acylation products and the removal of migrated phenols is extremely difficult. The azide type acylating agents are explosive, in general, and hence should be stored, handled and reacted under strictly controlled condi tions. Further, the benzyland t-alkyl-chloroformates, which may nuclear substituted, have such drawback that in case amines or hydrazides to be treated, e.g. amino acids, have other active groups in addition to amino and/or imino groups to be acylated, i.e., in case the amino acids are, for example, serine or threonin having hydroxyl groups, cystein having mercapto groups, and histidine having imidazole groups, the above-mentioned chloroformates react not only with the amino and/or imino groups but also with the said other active groups, so that the active groups other than the amino and/or imino groups to be acylated would have previously been protected by other protective groups.

With an aim to overcome the various drawbacks of the known acylating agents, the present inventors made extensive studies with respect to the functions and production processes of pyrimidyl thiolcarbonate to find that the aforesaid thiolcarbonates are suitable for various useful applications and have markedly excellent functions as acylating agents for introducing N- protective groups into amines and hydrazines, particularly amino acids and peptides, and that the thiolcarbonates can be easily produced on commercial scale. Based on the above finding, the inventors have accomplished the present invention.

The above-mentioned thiolcarbonates are novel compounds, and processes for acylating amines are hydrazines by use of such novel compounds have not been proposed yet.

An object of the present invention is to provide novel thiolcarbonates.

Another object of the invention is to provide a process for producing the novel thiolcarbonates.

A further object of the invention is to provide a process for acylating amines and hydrazines by use of said novel thiolcarbonates which have overcome various drawbacks of the known acylating agents.

Other objects and advantages of the present invention will become apparent from the description made hereinbelow.

The novel thiolcarbonates according to the present invention are represented by the formula,

wherein R and R are individually a hydrogen atom or a methyl group; and R is a straight chain or branched chain saturated or unsaturated alkyl group having 1 to 5 carbon atoms, or a benzyl or benzhydryl group which may be nuclear substituted.

In the above, the alkyl group includes, for example, methyl, ethyl, propyl, isopropyl, allyl, butyl, t-butyl, amyl and t-amyl groups, and the benzyl group which may be nuclear substituted includes, for example, benzyl, p-methoxybenzyl, 2,4-dimethoxybenzyl, 2,4,6- trimethoxybenzyl p-nitrobenzyl, p-chlorobenzyl and p-bromobenzyl groups.

Some examples of the compounds represented by the formula (I) are methyl pyrimidyl-2-thiolcarbonate, methyl 4-methyl-pyrimidyl-2-thiolcarbonate and methyl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate; and ethyl pyrimidyl-2-thiolcarbonate, propyl pyrimidyl-2-thiolcarbonate, isopropyl pyrimidyl-Z-thiolcarbonate, allyl pyrimidyl-Z-thiolcarbonate, n-butyl pyrimidyl-Z-thiolcarbonate, t-butyl pyrimidyl-Z-thiolcarbonate, n-amyl pyrimidyl-2-thiolcarbonate, t-amyl pyrimidyl-2-thiolcarbonate, benzyl pyrimidyl-2-thiolcarbonate, p-methoxybenzyl pyrimidyl-2-thiolcarbonate, 2,4-dimethoxybenzyl pyrimidyl-2-thiolcarbonate, 2,4,6-trimethoxybenzyl pyrimidyl-2-thiolcarbonate, pnitrobenzyl pyrimidyl-2-thiolcarbonate, p-chlorobenzyl pyrimidyl-2-thiolcarbonate, p-bromobenzyl pyrimidyl-2-thiolcarbonate and benzhydryl pyrimidyl-Z-thiolcarbonate (in which thiolcarbonates having 4-methyl and 4,6-dimethyl substituents in the pyrimidyl rings have been omitted, but these are naturally included in the compounds of the present invention).

Among the thiolcarbonates represented by the formula (l), the t-alkyl type, nuclear substituted or unsubstituted benzyl type and benzhydryl type carbonates are particularly important as acylating agents for use in the synthesis of N-protected amino acids and N- substituted peptides. Typical examples of such thiolcarbonates are t-butyl pyrimidyI-Z-thiolcarbonate, t-butyl 4-methyl pyrimidyl-2-thiolcarbonate and t-butyl 4,6- dimethyl-pyrimidyl-2-thiolcarbonate; and t-amyl pyrimidyl-Z-thiolcarbonate, benzyl pyrimidyl-Z-thiol carbonate, p-methoxybenzyl pyrimidyl-Z-thiolcarbonate, 2,4-dimethoxybenzyl pyrimidyl-Z-thiolcarbonate, 2,4,6-trimethoxybenzyl pyrimidyl-Z-thiolcarbonate, p-

nitrobenzyl pyrimidyl-2-thiolcarbonate, p-chlorobenzyl pyrimidyl-2-thiolcarbonate, p-bromobenzyl pyrimidyl-2-thiolcarbonate and benzhydryl pyrimidyl-2-thiolcarbonate (in which thiolcarbonates having 4-methyl and 4,6-dimethyl substituents in the pyrimidyl rings have been omitted, but these are naturally included in the compounds of the present invention.

In the t-alkyl type, nuclear substituted or unsubstituted benzyl type and benzhydryl type thiolcarbonates represented by the formula (I), those having methyl groups at the 4 and 6 positions of a pyrimidyl ring are most preperable since they show moderate activities in aminolysis of amino acids or peptides.

The thiolcarbonates represented by the formula (I) can be easily produced on commercial scale from inexpensive industrial reagents, as will be mentioned later. Further, the thiolcarbonates are stable compounds and hence can be easily stored and handled and, moreover, the thiolester portions thereof are extremely high in activity. Accordingly, they are particularly preferable as acylating agents for compounds having amino and/or imino groups.

The thiolcarbonates represented by the formula (I) can be easily produced on commercial scale according to the below-mentioned two processes, using as starting materials 2-mercapto-4- and/or 6-methyl-substituted or unsubstituted pyrimidines:

a. A process carried out by reacting a 2-mercapto4- and/or -methyl-substituted or unsubstituted pyrimidine with an alkali, reacting the resulting alkali metal salt of said pyrimidine with phosgene and then reacting the resulting pyrimidyl thiolchloroformate with an alcohol, or

b. A process carried out by reacting a 2-mercapto-4- and/or -methyl-substituted or unsubstituted pyrimidine with a halocarbonic acid ester.

The process (a) is explained in further detail below.

As is clear from the reaction schema shown below, the desired compound (I) is obtained by reacting an alkali metal salt represented by the formula (II) with phosgene, and reacting the resulting thiolchloroformate represented by the formula (III) in the presence of a base with an alcohol represented by the formula (IV).

sM S-C-Cl (II) (III) 1 N O H OH IV ll 3 l yew-041 Base N wherein R R and R are as defined in the formula (I), and M is an alkali metal, preferably lithium, sodium or potassium.

In the above-mentioned process, the alkali metal salt represented by the formula (II) is easily formed by dissolving a 2-mercapto-4- and/or 6-methyl-substituted or unsubstituted pyrimidine in an aqueous solution of an alkali metal hydroxide, preferably lithium hydroxide, sodium hydroxide or potassium hydroxide, at a concentration of preferably 10 to 50 by weight. After the dissolution, the aqueous solution is charged into a large amount of acetone to deposit the said alkali metal salt as a precipitate, which is then recovered by filtration and then dried, for example, at 120C. under reduced pressure, whereby the alkali metal salt of pyrimidine can be obtained in the form of a powder or mass.

The above-mentioned 2-mercapto-4- and/or 6-methyl-substituted or unsubstituted pyrimidine, e.g., 2-mercapto-pyrimidine or 2-mercapto-4-,6dimethylpyrimidine, can be easily prepared according to a known process from l,l,3,3-tetraethoxypropane and thiourea or from acetylacetone and thiourea, respectively, in the presence of hydrochloric acid as a catalyst.

The reaction of the alkali metal salt represented by the formula (ill) with phosgene is carried out by adding the alkali metal salt (ll) to a phosgene solution under cooling, preferably under cooling at 40 to +5C., and then stirring the resulting mixture at an optional temperature below the reflux temperature of the solvent, preferably at 0 to 40C. However, the said reaction sufficiently progresses even at about room temperature, and hence is ordinarly effected at a temperature about room temperature to 30C.). The reaction time varies depending on the kind of the alkali metal salt (ll) and on the reaction temperature, but is ordinarily from 10 to 120 minutes. The amount of phosgene used is preferably about l to 2 moles per mole of the said alkali metal salt (ll). This amount, however, is not critical, and phosgene may be used in an amount of more than 2 moles per mole of the alkali metal salt (II). The solvent for phosgene may be any solvent so far as it is inert to the reactants and to the reaction product, and is preferably petroleum ether, ether, benzene, toluene, methylene chloride, xylene, chloroform or tetrahydrofuran, for example.

After completion of the above-mentioned reaction, excess phosgene is removed by a suitable procedure, e.g. by injection of nitrogen at a temperature of 50 to 60C. Subsequently, the reaction liquid is cooled to room temperature and then filtered, and the filtrate is concentrated under reduced pressure in an inert gas such as nitrogen, whereby a crude pyrimidyl thiolchloroformate in the form of a liquid which is represented by the formula (III) is obtained in a yield of about 80 to 90 a The thiolchloroformate represented by the formula mate ill) is ordinarily used in a crude form, and the reaction liquid of pyrimidyl thiolchloroformate prior to concentration is sometimes used as it is. Among the pyrimidyl thiolchloroformates (lll), however, J 4,6- dimethyl-pyrimidyl-2-thiolchloroformate can be recovered in the form of crystals at a temperature below about 5C., and therefore the thus recovered crystals may be subjected to the subsequent reaction.

The reaction of the pyrimidyl thiolchloroformate represented by the formula (lit) with the alcohol represented by the formula R -OH (IV) is carried out by dissolving in an inert solvent the alcohol (IV) and a base as a deacidifying agent, dropping into the resulting solution under cooling, preferably at a temperature of -5 to +5C., the pyrimidyl thiolchloroformate (Ill) obtained by the aforesaid reaction, and heating the resulting mixture at a temperature below the reflux temperature of the solvent. This reaction, however, proceeds sufficiently quickly even at about room temperature and hence is ordinarily effected at a temperature about room temperature. The reaction time is ordinarily within the range from 2 to 24 hours.

Examples of the alcohol of the formula (IV) include alkyl alcohols such as methanol, ethanol, n-propanol, iso-propanol, allyl alcohol, n-butanol, t butanol, amyl alcohol and t-amyl alcohol, and benzyl alcohols and benzhydrols which may have been nuclear substituted such as benzyl alcohol, anise alcohol, 2,4- dimethoxybenzyl alcohol, 2,4,6-trimethoxybenzyl alcohol, p-nitrobenzyl alcohol, p-chlorobenzyl alcohol and p-bromobenzyl alcohol.

As the solvent, any solvent is usable so far as it is inert to the reactants and the reaction product, and ether, benzene, toluene, xylene, methylene chloride, chloroform, petroleum benzene, tetrahydrofuran or other saturated hydrocarbon, for example, is preferable.

As the deacidifying agent, any of those which are or dinarily used in this technical field is usable, and there may be used a tertiary amine such as, for example, triethylamine, N-alkylmorpholine, N,N-dialkylaniline, pyridine or quinoline.

Alternatively, the above reaction may be effected without the use of the above-mentioned solvent, while making the said tertiary amine display the actions of both the solvent and the deacidifying agent. Particularly when t-butanol, t'amyl alcohol or the like tertiary alkyl alcohol, which is great in steric hindrance and low in reactivity, is used in the reaction, it is preferable to adopt the process in which the above-mentioned tertiary amine is used as a solvent.

After completion of the reaction, the precipitate formed is separated by filtration, and the filtrate is washed and dried according to an ordinary procedure. For example, the filtrate is washed with a cold aqueous hydrochloric acid solution and an aqueous sodium chloride solution, and then dried over anhydrous sodium sulfate. Thereafter, the solvent is removed by distillation under reduced pressure whereby the desired thiolcarbonate represented by the formula (I) in the form of crude crystals is obtained in such a high yield,

as or more, in general. The thus obtained crude crystals are ordinarily purified by recrystallization from a suitable solvent such as, for example, petroleum ether, a hydrocarbon, ethyl acetate, benzene and water-alcohol mixture. in case a tertiary amine is used as a solvent, it is preferable that the filtrate after separation of precipitate is charged with the said inert solvent 7 8 and then subjected to the same washing, drying, solvent dispersing the aforesaid mercapto-pyrimidine (V) in a removal distillation and recrystallization as above. solvent, dropping into the resulting solution or disper- The aforesaid process (b) is explained in furthe d sion the halocarbonic acid ester with stirring at a low tail below. temperature, preferably at a temperature of to According to the process (b), the thiolcarbonate rep- 5 +5C., and stirring the resulting mixture at a temperaresented by the formula (I) can be obtained by reacti ture below the reflux temperature of the solvent, profa 2-mercapto-4- and/or 6-methyl substituted or unsubrably rom 30 to 60C., for l to 2 o in g stituted pyrimidine (V) with a halocarbonic acid ester This reaction Pmgresses sufficiently quickly even at (VI) in an inert solvent in the presence of a base, as is about room temperature, and hence y be Conducted elear f h reaction schema shown b l 10 at a temperature about room temperature l5 to (v) (VI) The solvent to be used may be of inert solvents which are insoluble in water, and includes, for example, meth- 5 ylene chloride, chloroform, ether, benzene, petroleum ether, petroleum benzene, toluene, xylene and tetrahydrofuran. Among these, methylene chloride and chloroform are preferable because they can make the reaction time. shorter and can make the yield higher.

30 After completion of the reaction, the organic phase is washed and dried according to an ordinary procedure. For example, the organic phase is washed with water or an aqueous sodium chloride solution and then wherein R R and R are as defined in the formula (I), and X is a halogen atom, preferably chlorine, bromine or fluorine.

As the halocarbonic acid ester represented by the formula (VI), chlorocarbonic acid ester, bromocarbonic acid ester or fluorocarbonic acid ester is preferable, especially chlorocarbonic acid ester is more preferable.

Examples of the chlorocarbonic acid ester of the formula (Vl) include methyl chlorocarbonate, ethyl chlorocarbonate, propyl chlorocarbonate, isopropyl chlorocarbonate* anyl chlorocarbonatei nbutyl chlorocar' dried over anhydrous sodium sulfate. Subsequently, the

bonate t'butyl chlorocarbonate namyl chlorocarb' 3S solvent is concentrated under reduced pressure to obndte t'amyl chlorocarbonate, benzyl chlorocarbonatei tain the desired thiolcarbonate represented by the forp-methoxybenzyl chlorocarbonate, 2,4- mula dhhethoxybehzyl chlomcarbonaiet 274,6 On the other hand, in case an inorganic base is used tnmethoxybenzyl chlorocarbonate, p-mtrobenzyl chloas a base, h tion is carried out by dissolving the rocarbonate, p-chlorobenzyl chlorocarbonate, p- 40 for said apto-pyrimidine (V) in an aqueous albfomobehzyl ehloroearbohate and behzhydryl Chloro kali solution at a concentration of about 10 to 50 Carbonate dropping into the resulting solution a solution of the These compounds are Prepared accorqlmg a halocarbonic acid ester in a solvent under stirring at a known p For example, chlorocarbonic acld low temperature, preferably at a temperature of 5 to ters are easily Prepared from alcohols and Phosgene, as +5C., and stirring the resulting mixture at a temperais well known. However, a chlorocarbonic acid ester of ture below the fl temperature f the Solvent, p.

8 y} alcohol, t-butanol or y alcohol, is erably from 30 to 60C., for 2 to 24 hours, in general. stable, in general, and hence should be handled at such This reaction proceeds sufficiently quickly even at a low temperature as below Thls halocarbomc about room temperature, and hence is carried out at a acid ester may be used without being isolated from the temperature about room temperature The amount f reaction h alkali used is preferably equivalent to or slightly excess The reaction of the p aI'd/0r 6'methyl' of the amount of said mercapto-pyrimidine. As the solsubstituted or unsubstituted pyrimidine with the vent, there is used the same solvent as in the case where halocarbonic acid ester (Vl) is carried out in an inert h for id organic b i used solvent in the presence of a base as a deacidifying agent Aft r Completion f h ti th r i ha at a temperature of Preferably from to 9 is washed and dried according to a suitable procedure. AS the base, there may be Used y 0f bases Which For example, the organic phase is successively washed are ordinarily LlSfid as agent in this techniwith 3 aqueous solutign and water or an aque- Ca fi Which include, for example, Organic bases Such ous sodium chloride solution, and then dried over anas the tertiary amines mentioned in the Process and hydrous sodium sulfate. Thereafter, the solvent is conihorgahie bases Such as a hydroxide, Carbonate of centrated to obtain the thiolcarbonate represented by carbonate of alkali metal, for example, sodium hydroxth f l (I), ide, potassium hydroxide, potassium carbonate, sodium A di to h process (b) h d i hi l carbonate, potassium bicarbonate and sodium bicarb t represented b th f la (I) can b bt i d bonate. in such a high yield as or more, in general, regard- In case a tertiary amine is used as a base (deacidiless of whether the base used is an organic or inorganic fying agent), the reaction is effected by dissolving or base. However, a t-alkyl 4- and/or 6-methyl-substituted or unsubstituted pyrimidyl-Z-thiolcarbonate, which is obtained by the reaction of a 2'mercapto-4- and/or 6-methyl-substituted or unsubstituted pyrimidine with a t-alkyl ester of halocarbonic acid, is low in yield, in

The base may be any of those which are ordinarily used in this technical field, and includes, for example, the tertiary amines and the like organic bases and inorganic bases which are used in the production of thiolgeneral. In order to increase the yield, therefore, it is carbonates represented by the formula (I). preferable to carry out the reaction at a low tempera- Generally, the above-mentioned reaction is carried out at a temperature ranging from 0 to 80C. Depend- The novel thlolcarbonates represeflted y the ing on the kind of the compound. having an amino or mula Which are Produced mg t0 t ab0 cimino group, however, the reaction may be conducted mentioned processes, are quite useful for protecting atatemperature below 0C. or above 80C. If the temwith groups of the formula perature is excessively low, the reaction rate becomes 0 extremely low, while if the temperature is excessively t high, side-reactions are undesirably brought about. in -C-O-R some cases. However, in case the compound having [5 amino and/or imino groups has other active group in the amino or imino groups of compounds having amino addition thereto, e.g., in case the said compound is any and/or imino groups, e.g., amines, hydrazines, amino of saccharides or steroids, the reaction is desirably caracids and peptides, and hence are used as acylating ried out at a temperature below 0C., particularly agents for the said compounds. below C. When the reaction is carried out at a In the next place, a process for acylating varous 20 temperature about room temperature, a reaction time amines and hydrazines by using as acylating agents the of more than 2 hours is required, in general. However, thiolcarbonates represented by the formula (I) is exwhen the reaction is conducted at such a high temperaplained below. ture as about 60C., the reaction is sufficiently com- The acylation process according to the present invenplete within 2 hours. tion comprises reacting the thiolcarbonate of the for- After completion of the reaction, the reaction prodmula (I) with a compound (VII) having amino and/or uct can be easily purified according to ordinary washimino groups in an inert organic solvent or in an aqueing, extraction and recrystallization. Particularly, the ous solution thereof in the presence or absence of a 2-mercapto-4- and/or G-methyI-Substituted or unsubstibase, as shown by the following reaction schema: tuted pyrimidine liberated in the above reaction is eas- R a- O N 3 Base H S-C--O-R HZ -----g R O--C-Z N R (1) (vii) (VIII) SH N) 2 wherein R R and R are as defined in the aforesaid formula (I), and H in the formula (VII) is a hydrogen atom in the amino or imino group of the compound of In the above reaction, the inert organic solvent may be any of water-soluble organic solvents which are inert to the reactants and the reaction product, and is preferably t-butyl alcohol, dioxane, tetrahydrofuran or dimethylformamide, for example.

ily soluble in acid or alkali, so that the reaction product can be readily purified by washing with a dilute aque ous acid or alkali solution.

Examples of the compound having amino and/or imino groups, which is represented by the formula (VII), include a wide scope of compounds such as aliphatic, alicyclic, aralkyl, aromatic and heterocyclic primary and secondary amines; hydrazines, and derivatives thereof; amino acids, peptides, and derivatives thereof; various saccharides and steroids having amino and/or imino groups. These amine compounds may contain, in addition to the amino and/or imino groups, other active groups such as, for example, alcoholic and- /or phenolic hydroxyl, mercapto, carboxyl, nitro or imidazole groups. However, it is natural that the introduc tion of acyl groups, particularly t-alkyloxycarbonyl groups, benzhydroxycarbonyl groups, and benzyloxycarbonyl groups, which may have been nuclear substituted, is most important for amino acids and peptides.

iii

In the examples shown later, therefore, the acylation of amino acids is explained chiefly, and the acylation of 'amines and hydrazines is explained with respect only to typical compounds. It will be understood from the above explanation and from the explanation made in the examples that the acylating agents of the present invention are concerned with the amino and/or imino groups of the compounds to be acylated and have nothing to do with the matrix structures of the compounds to be aminolyzed therewith. When the acylating agents of the present invention are used, any compounds having amino and/or imino groups can be acylated to give acylation products in high yields. Some examples of such compounds are as shown below.

As amino acids and derivatives thereof, there are used all the amino acids of natural occurrence and derivatives thereof. Concretely, these compounds inelude, for example, a-amino acids such as alanine (Ala), arginine (Arg), aspartic acid (Asp), asparagine (Asn), cysteine (Cys), cystine [(Cys) diiodotyrosine [Tyr (l glutamic acid (Glu), glycine (Gly), histidine (His), hydroxyproline (Hyp), isoleucine (lie), leucine (Leu), lysine (Lys), methionine (Met), norleucine (Nle), ornithine (Om), phenylalanine (Phe), proline (Pro), serine (Ser), threonine (Thr), tryptophan (Trp), tyrosine (Tyr) and valine (Val); B- and w-amino acids such as B-alanine, 'y-aminobutyric acid and e-aminocaproic acid; salts of said amino acids such as sodium, po-

tassium and magnesium salts; and derivatives of said acids such as acid esters and acid amides. Further, synthetic and semi-synthetic amino acids such as ozmethylalanine may also be used. It is natural that N- terminaI-free peptides obtained from two or more of the said amino acids are also usable.

As amines and hydrazines other than the abovemen- :tioned amino acids, there may be shown, for example, aliphatic and alicyclic primary and secondary amines such as methylamine, diemethylamine, ethylamine, 2- phenyl-ethylamine, ethanolamine, isopropylamine, tertiary butylamine, N-ethyl-N-B-hydroxyethylamine, octylamine, laurylamine and cyciohexylamine; primary and secondary aralkylamines and nuclear substituted derivatives thereof such as benzylamine, N- methylbenzylamine, p-nitrobenzylamine pchlorobenzylamine and 2-phenylethylamine; aromatic primary and secondary amines and nucleas substituted derivatives thereof such as aniline, Nmethylaniline, toluidine, xylidine, p-aminophenol, pmethylaminophenol, o-carbomethylaniline, pphenetidine, diphenylamine, oz- (and B-) naphthlamines and 4-aminonaphthol (l);heterocyclic primary and secondary amines such as ethyleneimine, pyrrolidine, pyrazole and indole, and nuclear substituted derivatives thereof; and hydrazines and derivatives thereof such as hydrazine, phenylhydrazine, 2,4-dinitrophenylhydrazine and N-methyl-N-phenylhydrazine.

As the saccharides and steroids, there may be used various sacchan'des and steroids having amino and/or imino groups such as 2-amino'l,6-anhydro-2-deoxy-B- D-glucopyranose, L-glucosamine and methyl-3-amino- B-L-xylopyranoside. In the acylation of these saccharides and steroids, particularly in the cases where they have other active groups in addition to amino or imino groups, it is required in most cases that only the amino or imino groups should be selectively acylated. When the acylating agents of the present invention is used, only the amino or imino groups can be selectively acylated even if said other active groups have not been protected at all.

In the acylation process according to the present invention, a compound having amino and/or imino groups is subjected to acylation reaction in the form of a free amine or of a salt thereof such as, for example, hydrochloride, hydrobromide, hydroiodide, sulfate or sulfite. In case the compound is subjected to the reaction in the form of a salt, the aforesaid deacidifying agent is required to be added to the reaction system.

According to the acylation process, in which the thiolcarbonate represented by the formula (I) is used as an acylating agent, the above-mentioned compound having amino and/or imino groups can be easily acylated under mild conditions to give a corresponding acylation product in such a high yield as more than about in general. The acylating agent of the present invention is well reactive with substantially all amine compounds. Further, the acylating agent of the present invention has such characteristic actions which are not seen in the conventional acylating agents that even though a compound having amino and/or imino groups, which is to be reacted therewith, additionally has in the molecule such active group as, for example, an alcoholic or phenolic hydroxyl, mercapto, carboxyl or imidazole group, the acylating agent reacts selectively with only the amino and/or imino groups.

The use of the acylating agent of the present invention brings about such advantage that the acylation product obtained by use of said acylating agent can be purified with extreme case. That is, in the aminolysis of the thiolcarbonate represented by the formula (I) by means of amino and/or imino groups, there are such characteristics that the 2-mercapto-4 and/or 6-methylsubstituted or unsubstituted pyrimidine is liberated with the progress of the reaction and that the said mercapto-pyrimidine is an amphoteric compound and is easily soluble in acid or alkali, so that it can be easily removed by washing said solution phase with a dilute aqueous acid or alkali solution, with the result that an extremely high purity acylation product can be obtained. In some cases, the produced mercaptopyrimidine is precipitated with the progress of the reaction. The precipitated mercapto-pyrimidine is filtered off and the filtrate is purified by washing with a dilute acid or alkali solution as mentioned above. The recovered mercapto-pyrimidine can be reused as a starting material for the production of the acylating agent ofthe present invention.

In the attached drawings, FIG. 1 is the infrared spectrum of 4,o-dimethyl-pyrimidyl-2-thiolchloroformate, the intermediate for the production of the thiolcarbonates of the formula (I). FIG. 2 FIG. 7 are the infrared spectra of the thiolcarbonates of the formula (I). FIG. 8 FIG. 22 are the infrared spectra of the acylated products obtained by using the thiolcarbonates of the formula (I) as acylating agents.

Procedures for preparing 2-mercapto-4- and/or 6-methyl-substituted or unsubstituted pyrimidines and thiolchloroformate thereof which are starting materials or intermediates for production of the present thiolcarbonates represented by the formula (I) are explained below with reference to referential examples.

REFERENTIAL EXAMPLE I 13 Synthesis of 2-mercapto-pyrirnidine:

A solution of 61 g. (0.80 mole) of thiourea in 600 ml. of ethanol was charged into a 2-liter three-necked flask equipped with a stirrer and a reflux condenser, and 200 ml. of concentrated hydrochloric acid was added to the solution, whereby the liquid became homogenous after several minutes. This liquid was mixed with 176 g. (0.80 mole) of l,1,3,3-tetraethoxypropane, and the resulting mixture was reacted under reflux for about 1 hour. After completion of the reaction, the reaction liquid was cooled to 10C. in an ice bath and maintained at said temperature for 30 minutes to deposit Z-mercapto-pyrimidine hydrochloride in the form of yellow crystals. The crystals were collected in a Buchner funnel, washed with 100 ml. of cold alcohol and then dried at room temperature to obtain 89 got crude 2-mercapto-pyrimidine hydrochloride in yield of 75 25 Grams (0.17 mole) of the above-mentioned crude Z-merQaptO-pyrimidine hydrochloride was suspended in 50 ml. of water, and the resulting suspension was ad justed to pH 7 to 8 by addition of 27 ml. ofa 20 aqueous sodium hydroxide solution, whereby Z-mercaptopyrimidine was precipitated. This mercaptopyrimidine was recovered by filtration with a Buchner funnel, washed with 50 ml. of cold water and then recrystallized from a solution comprising 300ml. of water and 300 ml. of ethanol to obtain 19 g. of 2-mercaptopyrimidine in yield of 70 Elementary analysis:

Calcd. C: 42.84 H: 3.59 N: 24.98 S: 28.59

(for C.,l-l N S) Found C: 42.91 H: 3.68 N: 24.92 S: 28.48

REFERENTIAL EXAMPLE 2 Synthesis of 2-mercapto-4,6-dimethyl-pyrimidine:

76 Grams (1.0 mole) of thiourea was suspended in a solution of 120 g. 1.2 mole) of acetylacetone in 2,500 ml. of ethanol. The resulting suspension was mixed with 250 ml. of concentrated hydrochloric acid, and then reacted under reflux for 2 hours. After completion of the reaction, the reaction liquid was cooled, whereby beautiful yellow needle-like crystals of 2-mercapto-4,6- dimethyl-pyrimidine hydrochloride were formed. The reaction liquid was allowed to stand overnight to sufficiently deposit the crystals, which were then recovered by filtration and dried to obtain 140 g. of 2-mercapto- 4,6-dimethyl-pyrimidine hydrochloride in yield of 80 To the filtrate after recovery of the abovementioned pyrimidine hydrochloride were again added 110 g. of acetylacetone, 76 g. of thiourea, 100 ml. of ethanol and 150 ml. of concentrated hydrochloric acid, and the resulting mixture was subjected to filtration and drying to obtain 158 g. of 2-mercapto-4,6-dimethyl-pyrimidine hydrochloride in yield of 90 The filtrate in this case was again subjected to the same operation as above to obtain 148 g. of 2-mercapto-4,6-dimethyl-pyrimidine hydrochloride in yield of 84 7a.

200 Grams (1.13 moles) of the above-mentioned 2- mercapto-4,6-dimethyl-pyrimidine hydrochloride was suspended in 400 ml. of water, and the resulting suspension was heated to about 40C. while gradually adding thereto 70 ml. of a 20 aqueous sodium hydroxide solution, whereby the 2-mercapto-4,6-dimethylpyrimidine hydrochloride was completely dissolved. This solution was adjusted to pH 4.5 to 5.0 by gradual addition of a 20 aqueous sodium hydroxide solution, whereby pale yellow crystals of 2-mercapto-4,6- dimethyl-pyrimidine were precipitated. The reaction liquid was allowed to stand overnight at room temperature to sufficiently deposit the crystals, which were then recovered by filtration and dried to obtain 11 7 g. of 2-mercapto-4,o dimethyl-pyrimidine in yield of 74.3 4

Elementary analysis: Calcd. C: 51.40 H: 5.75 70, N: 19.98 70, S: 22.87

(for C H N S) Found C: 51.52 H: 5.75 N: 20.03 70, S: 22.75

REFERENTlAL EXAMPLE 3 Synthesis of 4,6-dimethyl-pyrimidyl-Z-thiolchloroformate:

A solution of 128 g. (3.2 moles) of sodium hydroxide in 600 ml. of water was mixed with. 420 g. (3 moles) of 2-mercapto-4,6-dimethyLpyrimidine, and the resulting mixture was heated to completely dissolve the dimethyl-pyrimidine and then allowed to cool. The resulting solution was charged into 15 liters of acetone, whereby a sodium salt of 2-mercapto-4,6-dimethyl-pyrimidine was precipitated. The precipitated sodium salt was recovered by filtration and then dried at 120C. for 24 hours to obtain 462 g. of said sodium salt in a solid form in yield of Subsequently, 324 g. (2moles) of the abovementioned sodium salt of 2-mercapto-4,6-dimethylpyrimidine was added as it was, i.e.,. in the form of solid, at 0 to 5C. to 990 g. of a 30 toluene solution of phosgene, and the resulting mixture was reacted with stirring at room temperature for 1 hour. After completion of the reaction, excess phosgene was removed by distillation at 50 to 60C., while injecting nitrogen into the reaction liquid. Thereafter, the precipitate formed was filtered and then the toluene was removed by distillation under reduced pressure to obtain about 365 g of 4,6-dimethyl-pyrimidyl-Z-thiolchloroformate in yield of 90 The thus obtained pyrimidyl-2-thiolchloroformate is hydrolyzed within a short period of time when allowed to stand in air, and hence should be stored in a water free state. Further, the said pyrimidyl-2-thiolchloroformate is decomposed when heated to above C, and therefore the purification thereof according to distillation was substantially impossible.

Infrared absorption spectrum of the abovementioned 4,6-dimethyl-pyrimidyl-2-thiolchloroformate is shown in FM]. 11. According to the said drawing,

specific absorptions derived from C O in the group of 0 ll .S..;C..

C1 in the group of I and pyrimidine ring of said compound are obviously recognized at 1775 cm, 800 cm" and 1587 cm" and 1253 cm, respectively.

Procedures for producing the present thiolcarbonates represented by the formula (I) are illustrated below with reference to examples.

EXAMPLE 1 Synthesis of ethyl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate:

20.3 Grams (0.44 mole) of dehydrated ethanol and 41.8 g. (0.528 mole) of pyridine were added to 650 ml. of ether. Into the resulting mixture was dropped under stirring and cooling to to 0C. 81.0 g. (0.40 mole) of the 4,6-dimethyl-pyrimidyl-2-thiolchloroformate obtained in Referential Example 3, and then the mixture was reacted at 20C. for 3 hours. After completion of the reaction, the reaction liquid was washed twice each with 100 ml. of a aqueous citric acid solution and 100 ml. of a saturated aqueous sodium chloride solution, and successively dried over anhydrous sodium sulfate and then the ether was removed by distillation to obtain 78.0 g. of ethyl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate in the form of syrup in yield of 92 When recrystallized from an ether-petroleum ether solvent, the product showed a melting point of 25C.

Elementary analysis:

Calcd. C: 50.93 H: 5.70 N:

Found C: 50.92 H: 5.69 N: 13.23

FIG. 2 shows the infrared spectrum of ethyl 4,6- dimethyl-pyrimidyl-2-thiolcarbonate. The infrared spectrum shows the presence of in the ester bond (1735 cm),

ll C-O- (1125 Cm 13.20 (for the pyrimidine ring (1586 and 1258 cm), and CH and C1-l groups (1440 and 1370 cm).

EXAMPLE 2 Synthesis of t-butyl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate:

Into a solution of 69.7 g. (0.94 mole) of t-butyl alcohol in 185.9 g of pyridine was dropped under stirring and cooling to -5 to 0C. 95 g. (0.47 mole) of the 4,6- dimethyl-pyrimidy1-2-thiolchloroformate obtained in Referential Example 3, and the resulting mixture was reacted at to C. for 3 hours. After the reaction, deposited pyridine hydrochloride was separated by tiltration. and the filtrate was charged with 500 ml. of water and then extracted 3 times each with 200 ml. of petroleum ether. The petroleum ether phase was sufficiently washed with a cold 1N aqueous hydrochloric acid solution, washed twice with an aqueous sodium chloride solution and dried over anhydrous sodium sulfate, and then the petroleum ether was removed by distillation under reduced pressure, whereby crystals were obtained.

The crystals were washed with a small amount of cold n-pentane and then dried to obtain 96 g. of t-butyl 4,6- dimethyl-pyrimidyl-Z-thiolcarbonate, yield 85 m.p. 50 51C.

Elementary analysis:

Calcd. C: 54.98 H: 6.71 N: 11.66 S: 13.34

116 (for C 1-l O N S) Found C: 54.88 H: 6.64 N: 11.57 S: 13.29

FIG. 3 shows the infrared spectrum of t-butyl 4.6- dimethyl-pyrimidyl-2-thiolcarbonate. The infrared spectrum shows the presence of 0 ll -0- in the ester bond (1743 cm),

11 -c-o- (1105 0m the pyrimidine ring 1587 and 1258 cm), and the deformation vibration of CH in -C(CH (1393 and 1370 cm").

EXAMPLE 3 Synthesis of t-amyl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate:

Into a solution of 26.4 g. (0.30 mole) of t-amyl alcohol in 61 ml. of pyridine was dropped under stirring and cooling to 5 to 0C. 30.4 g. (0.15 mole) of the 4,6- dimethyl-pyrimidyl-2-thiolchloroformate obtained in Referential Example 3, and the resulting mixture was reacted at 20 to 25C. for 3 hours. After the reaction, deposited pyridine hydrochloride was separated by filtration, and the filtrate was charged with 150 ml. of water and then extracted 3 times each was 60 ml. of petroleum ether. The petroleum ether phase was sufficiently washed with a cold 1N aqueous hydrochloric acid solution, washed twice with an aqueous sodium chloride solution and dried over anhydrous sodium sulfate, and then the petroleum ether was removed by distillation under reduced pressure to obtain 33.0 g. of tamyl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate in the form of syrup, yield Elementary analysis:

Calcd. C: 56.67 H: 7.13 N:

Found C: 56.70 H: 7.11 N: 11.03 7r FIG. 4 shows the infrared spectrum of t-amyl 4,6- dimethyl-pyrimidyl-2-thiolcarbonate. The infrared spectrum shows the presence of 11.01 (for in the ester bond (1730 cm),

0 H I l -G-=O-= (1112 cm the pyrimidine ring (1584 and 1259 cm and CH and -CH groups (1434 and 1368 cm).

EXAMPLE 4 Synthesis of n-butyl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate:

0.44 Mole of n-butanol and 0.528 mole of pyridine were added to 650 ml. of ether. Into the resulting mixture was dropped under stirring and cooling to 5 to 0C. 0.40 mole of the 4,6-dimethyl-pyrimidyl-2-thiolchloroformate obtained in Referential Example 3, and the mixture was reacted in the same manner as in Example 1. After the reaction, the reaction liquid was washed and dried in the same manner as in Example 1, and then the solvent was removed by distillation to obtain n-butyl 4.fi-dimethyl-pyrimidyl-2-thiolcarhonate in a high yield.

EXAMPLE 5 Synthesis of benzyl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate:

4.86 Grams (0.045 mole) of benzyl alcohol and 3.57 g. (0.045 mole) of pyridine were dissolved in 100 ml. of methylene chloride. Into the resulting solution was dropped under stirring and cooling to 5 to 0C. 8.10 g. (0.040 mole) of the 4,6-dimethyl-pyrimidyl-Z-thiol chloroformate obtained in Referential Example 3, and the resulting mixture was reacted at room temperature for 3 hours. After completion of the reaction, the reaction liquid was successively washed twice with each ml. of a 10 aqueous sodium chloride solution, a saturated aqueous sodium bicarbonate solution, a 10 aqueous sodium chloride solution, a 0.5 N aqueous hydrochloric acid solution and a 10 aqueous sodium chloride solution, and then dried over anhydrous sodium sulfate. Subsequently, the methylene chloride was removed by distillation, and the residue was recrystallized from an ether-petroleum ether solvent to obtain 1 1.2 g. of benzyl 4,6-dimethyl-pyrimidyl-Z-thiolcarbonate, yield 91.5 m.p. 934 94.5 C.

Elementary analysis:

Calcd. C: 61.29 H: 5.14 N: 10.21 S: 11.69

% (for C d-1 0 19 5) Found C: 61.12 H: 5.20 N: 10.40 8:11.98

FIG. 5 shows the infrared spectrum of benzyl 4,6 dimethyl-pyrimidyl-2-thio1carbonate. The infrared spectrum shows the presence of 0 ll .41 in the ester bond (1730 cm), v, 0 ll -c-o- (1107 cm the pyrimidine ring 1 584cm) and mono-substituted phenyl group (753 and 700 cnf).

EXAMPLE 6 Synthesis of p-methoxybenzyl 4,6-dimethylpyrimidyl-Z-thiolcarbonate:

61 Grams (0.44 mole) of anise alcohol and 41.8 g. (0.528 mole) of pyridine were dissolved in 650 ml. of ether. Into the resulting solution was dropped under stirring and cooling to 5 to 0C. 81.0 g. (0.40 mole) of the 4,6-dimethyl-pyrimidyl2-thiolchloroformate obtained in Referential Example 3, and the resulting mixture was reacted at room temperature for 3 hours. After the reaction, the reaction liquid was washed 2 times with a 10 aqueous citric acid solution and a sat- Calcd. C: 59.19 H: 5.30 /0, N: 9.20 S: 10.54

18 is m s z' l Found C: 58.98 70, H: 5.31 '71. N: 9.22 Z, S: 10.48 '7! FIG. 6 shows the infrared spectrum of pmethoxybenzyl 4,6-dimethylpyrimidyl-2-thiolcarbonate. The infrared spectrum shows the presence of in the ester bond (1720 cm),

ll -co- (1125 onf the pyrimidine ring (1586 and 1250 cm" ),OC1-l group (2830 andlsft ahstttqts n a up (828 cm EXAMPLE 7 Synthesis of p-chlorobenzyl 4,6-dimethyl-pyrimidyl-Z-thiolcarbonate:

EXAMPLE 8 Synthesis of p-nitr0benzyl 4,6-dimethyl-pyrimidyl- 2-thiolcarbonate:

p-Nitrobenzyl alcohol (0.44 mole) and 0.528 mole of pyridine were dissolved in 650 ml. of ether. Into the resulting solution was dropped under stirring and cooling to 5 to 0C. 0.40 mole of 4,6-dimethyl-pyrimidyl-2- thiolchloroformate obtained in Referential Example 3 and the resulting mixture was reacted in the same manner as in Example 6. After the reaction, the reaction liquid was washed and dried in the same manner as in Example 6, and then the solvent was removed by distil- .lation to obtain p-nitrobenzyl 4,6-dimethyl-pyrimidyl- Z-thiolcarbonate in a high yield.

EXAMPLE 9 Synthesis of benzhydryl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate:

36.85 Grams (0.20 mole) of benzhydrol and 17.40 g. (0.22 mole) of pyridine were dissolved in 450 ml. of ether, and the resulting solution was cooled to -5 to 0C. Into the solution was dropped a solution of 40.53 g. (0.20 mole) of 4,6-dimethyl-pyrimidyl-2-thiolchloroformate in 50 ml. of ether, and the mixed solution was reacted with stirring at 20C. for 4 hours. After the reaction, a pyridine salt form was suction-filtered, and the filtrate was washed twice at 0C. with 200 ml. of a 5 aqueous hydrochloric acid solution, once with 200 ml. of a 10 aqueous sodium bicarbonate solution and once with 200 ml. of a saturated aqueous sodium chloride solution, and dried over anhydrous sodium sulfate, and then the ether was removed by distillation to obtain FIG. 7 shows the infrared spectrum of benzhydryl 4,- 6-dimethyl-pyrimidyl-Z-thiolcarbonate. The infrared spectrum shows the presence of in the ester bond (1730 cm),

1 i-o- (1118 cm the pyrimidine ring 1586 cm) and mono-substituted phenyl group (761 and 700 cm).

EXAMPLE Synthesis of ethyl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate:

28 Grams (0.2 mole) of 2-mercapto-4,6-dimethylpyridine was added to 30 g. of a 50 aqueous potassium hydroxide solution. Into the resulting mixture was dropped under stirring and ice-cooling a solution of 21.7 g. of ethyl chlorocarbonate in 500 ml. of methylene chloride, and then the mixture was reacted at room temperature for 24 hours. After completion of the reaction. the methylene chloride phase was separated, washed twice with a saturated sodium bicarbonate solution and twice with a 10 aqueous sodium chloride solution, and dried over anhydrous sodium sulfate, and then the methylene chloride was concentrated to obtain 37.5 g. of ethyl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate in the form of syrup in yield of 88.4 When recrystallized from an ether-petroleum ether solvent, the product showed a melting point of 23 to 25C.

Elementary analysis:

Calcd. C: 50.93 H: 5.70 N:

Found C: 50.92 1-1: 5.69 N: 13.23

The infrared spectrum of the thus obtained compound is the same as shown in FIG. 2.

EXAMPLE 11 Synthesis of n-butyl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate:

13.20 (for 0.2 Mole of 2-mercapto-4,6-dimethy1-pyrimidine was added to g. of a 50 aqueous potassium hydroxide solution. Into the resulting mixture was dropped under stirring and ice-cooling a solution of 0.2 mole of n-butyl chlorocarbonate in 500 ml. of methylene chloride, and the mixture was reacted in the same manner as in Example 10. After the reaction, the reaction liquid was washed and dried in the same manner as in Example 10, freed from the solvent by distillation and then subjected to recrystallization to obtain n-butyl 4,6-

dimethyl-pyrimidyl-2-thiolcarbonate in a high yield.

Example 12 Synthesis of benzyl 4,o-dimethyl-pyrimidyl-2-thiolcarbonate:

70.1 Grams (0.5 mole) of 2-mercapto-4,6-dimethylpyrimidine was added to 56.1 g. of a 50 aqueous potassium hydroxide solution. Into the resulting mixture was dropped under stirring and ice-cooling a solution of 85.3 g. (0.5 mole) of carbobenzoxy chloride in 500 ml. of methylene chloride, and then the mixture was reacted at room temperature for 24 hours. After the reaction, the methylene chloride phase was separated,- washed twice with 50 ml. of a saturated sodium bicarbonate solution and twice with 50 ml. of a 10 aque ous sodium chloride solution, and dried over anhydrous sodium sulfate, and then the methylene chloride was concentrated to obtain 130 g. of crystalline benzyl 4,6- dimethyl-pyrimidyl-2-thiolcarbonate in yield of 94.9 When recrystallized from an ether-petroleum ether solvent, the product showed a melting point of 94 to 945C.

Elementary analysis:

Calcd. C: 59.19 H: 5.30 N:

Found C: 58.98 1-1: 5.31 N: 9.22

The infrared spectrum of the thus obtained compound is the same as shown in FIG. 5.

EXAMPLE 13 Synthesis of p-methoxybenzyl 4,6-dimethyl-pyrimidyl-2-thiolcarbonate1 9.20 (for Into a solution of 29 g. (0.29 mole) of phosgcne in ml. of methylene chloride was dropped under stirring at 30 to 10C. a solution of 32.5 ml. (0.26 mole) of p-methoxybenzyl alcohol in 100 ml. of methylene chloride, and the mixed solution was further stirred for 30 minutes. Subsequently, nitrogen gas was injected to remove excess phosgene, and the resulting pmethoxybenzyloxy carbonyl chloride solution was mixed with 42.0 g. (0.3 mole) of 2-mercapto-4,6- dimethyl-pyrimidine. Into this mixture was dropped a solution of 84 ml. (0.6 mole) of triethylamine in 100 ml. of methylene chloride. Thereafter, the temperature was gradually elevated to room temperature, and the mixture was reacted at room temperature for 4 hours. After the reaction, the methylene chloride was concen trated and then 200 ml. of ether and 100 ml. of water were added to the reaction liquid. Subsequently, the ether phase was separated, washed twice with 20 m1. of a cold 10 aqueous citric acid solution and 20 ml. of a saturated aqueous sodium chloride solution and dried over anhydrous sodium sulfate, and then the ether was concentrated to obtain 70.5 g. of pmethoxybenzyl 4,6- dimethyl-pyrimidyl-2-thiolcarbonate in yield of 81.0 When recrystallized from an ether-petroleum ether solvent, the product showed a melting point of 58 to 60C.

Elementary analysis:

Calcd. C: 59.19 71, H: 5.30 7r, N: 9.20 71 (for Found C: 58.98 X, H: 5.31 70, N: 9.22 /1 The infrared spectrum of the thus obtained compound is the same as shown in FIG. 6.

21 EXAMPLE 14 The p-chlorobenzyloxy carbonyl chloride solution with 50 ml. of a saturated aqueous sodium chloride solution and dried over anhydrous sodium sulfate. and then the ethyl acetate was removed by distillation under reduced pressure, whereby a syrupy residue was obtained. This residue was dissolved in 65 ml. of ethaprepared by the same procedure as 1n Example 13 was nol, and the resulting solution was charged with 50 ml. i .wlth mole z'mfercapto'db'dlmethyl of water and then cooled to obtain 11.3 g. of crystals pymlndme' the msultlng mlxtufe w dropped a of N-t-butyloxycarbonyl-Lleucine monohydrate, yield solution of 0.6 mole of trlethylam ne 1n 100 ml. of 973 to [gradually melting at about methylene chlorlde, and then the m1xture was reacted 9 Journal f A i Chemical Society. 79, 1n the same manner as 1n Example 13. After the reac- 6180 7 tion, the reaction liquid was washed and dried in the Elemental-y analysis; same manner as 1n Example 13, concentrated and then Calcd 5299 H; 930 5.62 recrystallized to obtain p-chlorobenzyl 4,6-dimethyl- Found C: 5288 921 N: 5.68 pyrimidyl-2-thiolcarbonate in a high yield.

EXAMPLE 17 EXAMPLE l5 Example 16 was repeated, except that each of so- P p'mtrobenzyl dium hydroxide, triethylamine, sodium carbonate and 46'dlmethyl'pynmldyl'2thwlcarbmate: sodium bicarbonate was used as the base; each of diox- The p-nitrobenzyloxy carbonyl chloride solution pre- 20 fi e, t-but and thy f d was pared by the same procedure as in Example 13 was used as the solvent; and the molar ratio (AA/base) of mixed with 0.3 mole of 2-mercapto-4,6-dimethylbase to L-leucine and the reaction temperature and pyrimidine. Into the resulting mixture was dropped a time were varied as shown in Table 1. The yields of the solution of 0.6 mole of triethylamine in 100 ml. of resulting N-t-butyloxycarbonyl-L-leucine were as set methylene chloride, and then the mixture was reacted forth in Table 1, provided that the yields are values of in the same manner as in Example 13. After the reacproducts prior to recrystallization.

Table 1 Base M21011 N(c.H.1. Nmco. NaHco. A.A./Base 1.0/1.1 1.0/1.5 1.0/1.1 1.0/15 1.0/1.1 1.0/1.1 Reaction temp.(C.) -35 30-35 15-20 30-35 40-45 30-35 30-35 Reaction 1 time 111. 2 5 10 10 10 5 10 2.5 10 10 Solvent Dioxane 80.3% 84.4% 87.5% 95.8% 82.7% 90.3% 100% 85.2% 20.6% t-Butanol 74.4% 86.1% 86.4% 86.5% 95.8% D.M.F. 86.4% 91.2% 79.3% 98.6% 100% 92.0%

tion, the reaction liquid was washed and dried in the EXAMPLE 18 same manner as in Example 13, concentrated and then s recrystallized to obtain p-nitrobenzyl 4,6-dimethylsynthesls of N t butyloxycarbony l L alanme' pyrimidyl-Z-thiolcarbonate in a high yi ld 4.46 Grams (0.050 mole) of L-alanlne and 10.5 ml.

Applications as acylating agents of the thiolcarbonates represented by the formula (I) are explained below with reference to examples.

EXAMPLE 16 Synthesis of N-t-butyloxycarbonyLL-leucine:

6.56 Grams (0.050 mole) of L-leucine and 10.5 ml. (0.075 mole) of triethylamine were added to 27.5 ml. of water. To the resulting mixture was added a solution of 13.2 g. (0.055 mole) of t-butyl 4,6-dimethylpyrimidyl-2-thiolcarbonate in 27.5 ml. of dioxane, and then the mixture was reacted under stirring at room temperature for 10 hours. After completion of the reaction, 75 ml. of water was added to the reaction liquid, and unreacted thiolcarbonate was extracted thrice with 100 ml. of ethyl acetate. Subsequently, the aqueous phase was cooled to 0C.. adjusted to pH 3 by addition of a saturated aqueous citric acid solution, and then extracted once with 75 ml. of ethyl acetate and twice with (0.075 mole) of triethylamine were added to 27.5 ml. ml. of water. To the resulting mixture was added the same dioxane solution of t-butyl 4,6-dimethylpyrimidyl-Z-thiolcarbonate as in Example 16, and the mixture was reacted under stirring at room temperature for 10 hours. After completion of the reaction, the reaction liquid was extracted, washed and dried in the same manner as in Example 16, and then the ethyl acetate was removed by distillation to obtain 9.38 g. of crystals of N-t-butyloxycarbonyl-L-alanine in yield of 99.2 When recrystallized from an ethyl acetatepetroleum ether solvent. the product showed a melting 'point of 810 to 820C. [Journal of Chemical Society EXAMPLE 19 Synthesis of dicyclohexylamine salt of N.-t-butyloxy-carbonyl-L-tyrosine:

9.05 Grams (0.050 mole) of L-tyrosinc and 17.5 ml.

23 24 (0.125 mole) of triethylamine were added to 27.5 ml. of water. To the resulting mixture was added the same i dioxane solution of t-butyl 4,6-dimethyl-pyrimidyl-2- d thiolcarbonate as in Example 16, and the mixture was m the Carboxyl group (1518 cm m reacted under stirring at room temperature for 24 5 H hours. After completion of the reaction, the reaction liquid was extracted, washed and dried in the same manner as in Example 16. The thus treated liquid was m the amide bond 2 Cm added to a solution of 8.46 g. (0.050 mole) of dicy- 9 Shows the presence 0 clohexylamine in 500 ml. of ethyl acetate, and the re- O sulting mixture was allowed to stand overnight in a cold ll place, whereby crystals were deposited. The crystals were recovered by filtration and then washed with ethyl in the carboxyl group l 737 cm) and acetate to obtain 27.29 g. of a dicyclohexylamine salt 0 ,0 of N-t-butyloxycarbonyl-L-tyrosine, yield 99.2 m.p. H il 208C. (decomp0sition)[.lournal of Chemical Society -C- in the C-N 2632 -lbond (1638 cm).

Elementary analysis: FIG. shows the presence of NH (3452 cm" illCd- C 67-50 H N1 605 OH in the H 0 (3375 cm, broad absorption), Found C: 67.47 71. H: 9.17 '71, N: 5.98 V: 0 liXAMlLl-I g In the same manner as in Example [8 or 19, various h 7 I amino acids shown in Table II were reacted with tas m thb unboxyl group (I708 and butyl 4,6-dimethyl-pyrimidyl-Z-thiolcarbonate in the 0 presence of triethylamine, and the reaction products 2 were extracted and purified to obtain corresponding N-t-butyloxycarbonyl amino acids. Provided that in m the am'de bond (1664 Cm Run No. 3, ether was used as a precipitant for dicy- 11 shows the presence of NH (3300 Cm clohexylamine salt. The results obtained were as set 0 forth in Table II. II

FIG. 8 FIG. 11 show the infrared spectra of BOC-LIle-OH (monohydrate)(No. 2), m the carboxyl g p (1705 and BOC-LProOI-I (No. 4), BOC-L-Ser-OH (V2 0 hydrate) (No. 5) and BOCLValOI-I (No. 7), ll shown in Table II, respectively. C-

FIG. 8 shows the presence of NH (3300 cm), i h amide bond (1645 cm).

Table II I I i t 'nt 0 Run Amino N-t-Butyloxy Yield Mel lng pol Remarks NO acid carbonyl I amino acid Present Literature invention value *3) l Gly-OH BO0 -Gly-OH 92.0 87.0-89.0 94-95 Process of Example 18 BOG-L-Ile-OH u n 2 L-IlG-OH (monohydrate) 100 68.0-71.0 66-68 BOG-L-Met-OH 5 L-l Iet-OH *2) 100 135.5-159.0 158-159 Example 9 (DCHA 4 L-PIo-OH BOC-L-Pro-OH I .5 156 .0-l37.0 154-156 Example 18 BOC-LSerOH n n 5 L-Ser-OH y 84.6 86.0-71.0 75-78 6 L-Trp-OH BOC-L-Trp-OH l37-O-l38.0 155-137 I 7 L-Val-OH BOC-L-Val-OH 98.6 76 5-78.6 72-73 *1) B00: t-Butyloxycarbonyl group (CH )O-C-) DCHA: Dicyclohexylamine salt Literature:

EXAMPLE 21 Synthesis of dicyclohexylamine salt of N-t-amyloxycarbonyl-L-alanine:

4.46 Grams (0.050 mole) of L-alanine and 10.5 ml. (0.075 mole) of triethylamine were added to 27.5 ml. of water. To the resulting mixture was added a solution of 14.0 g. (0.055 mole) of t-amyl 4,6-dimethylpyrimidyl-2-thiolcarbonate in 27.5 ml. of dioxane, and I the mixture was reacted under stirring at room temperature for 24 hours. After completion of the reaction, the reaction liquid was extracted, washed and dried in the same manner as in Example 16, and then charged with 8.46 g. (0.050 mole) of dicyclohexylamine and with petroleum ether to precipitate 18.25 g. of a dicyclohexylamine salt of N-t-amyloxycarbonyl-L-alanine in yield of 98.1 When recrystallized from an etherpetroleum ether solvent, the product showed a melting point of 125 to 127C. [Bulletin of the Chemical Society oflapan, 38(9), 1522 (1965): 124-126C.].

Elementary analysis:

Calcd. C: 65.58 H: 10.48 N: 7.55

Found C: 65.73 H: 10.35 N: 7.41

EXAMPLE 22 Synthesis of dicyclohexylamine salt of N-t-amyloxy-carbonyl-L-tyrosine:

9.05 Grams (0.05 mole) of L-tyrosine and 17.5 ml. (0.125 mole) of triethylamine were added to 27.5 ml. of water. To the resulting mixture was added the same dioxane solution of t-amyl 4,6-dimethyl-pyrimidyl-2 -thiolcarbonate as in Example 21, and the mixture was reacted in the same manner as in Example 21. After completion of the reaction, the reaction liquid was extracted, washed and dried in the same manner as in Example 16. The thus treated liquid was charged with a solution of 8.46 g. (0.050 mole) of dicyclohexylamine in 500 ml. of ethyl acetate and with petroleum ether, and the resulting mixture was allowed to stand in a cold place, whereby crystals were deposited. The crystals were recovered by filtration and then washed with ethyl acetate to obtain 23.88 g. of a dicyclohexylamine salt of N-t-amyloxycarbonyl-L-tyrosine, yield 98.7 mp. 202C. (decomposition).

Elementary analysis:

Calcd. C: 68.11 H: 9.30 N: 5.88

Found C: 68.23 H: 9.28 N: 5.79

EXAMPLE 23 Synthesis of N-Carbobenzoxy-benzylamine:

To a solution of 1.07 g. (0.01 mole) of benzylamine in ml. of ether was added at room temperature a solution of 2.74 g. (0.01 mole) of benzyl 4,6-dimethylpyrimidyl-2-thiolcarbonate in 10 ml. of ether, and the mixed solution was reacted under stirring for 30 minutes. With progress of the reaction, 2-mercapto-4,6 dimethyl-pyrimidine was liberated to form a precipitate. The precipitate was separated by filtration, and the filtrate was washed twice with 10 ml. of a 1N aqueous hydrochloric acid solution and 10 ml. of a 10 7( aqueous sodium chloride solution and dried over anhydrous sodium sulfate, and then the ether was concentrated to obtain crystalline N-carbobenzoxy benzylamine quantitatively. When recrystallized from an ether-petroleum ether solvent, the product showed a melting point of 61 to 62C.

Elementary analysis: Calcd. C: 74.67 H: 6.27 N

Synthesis of N-carbobenzoxy-btryptophan:

2.04 Grams (0.01 mole) of L-tryptophan and 1.67 g. (0.012 mole) of triethylamine were added to 8 ml. of water. To the resulting mixture was added a solution of 3.01 g. (0.01 1 mole) of benzyl 4,6-dimethyl-pyrimidyl- 2-thio1carbonate in 16 ml. of dioxane, and the mixture was reacted under stirring at 60 to 65C. for 2 hours. After completion of the reaction, the dioxane was removed by distillation under reduced pressure, and 15 ml. of water was added to the residue. Thereafter, the unreacted thiolcarbonate was extracted with ethyl acetate, and the aqueous phase was adjusted to pH 3 by addition of a saturated aqueous citric acid solution, and then extracted once with 15 ml. of ethyl acetate and twice with 8 ml. of ethyl acetate. Subsequently, the ethyl acetate phases were united together, washed once with 10 ml. of a 1N aqueous hydrochloric acid solution and twice with 10 ml. of a saturated aqueous sodium chloride solution and dried over anhydrous sodium sul fate, and then the ethyl acetate was removed by distillation under reduced pressure, whereby crystals of N-carbobenzoxy-L-tryptophan were obtained substantially quantitatively. When recrystallized from an etherpetroleum ether solvent, the product showed a melting point of 122 to 124C.

Elementary analysis:

Calcd. C: 67.59 H: 5.40 70, N: 8.15 "/0 Found C: 67.45 71, H: 5.36 7!, N: 8.28 "/1 EXAMPLE 25 Synthesis of N-p-methoxybenzyloxycarbonyl-L-alanine:

8.9 Grams (0.1 mole) of L-alanine and 21 ml. (0.15 mole) of triethylamine were added to 55 ml. of water. To the resulting mixture was added a solution of 33.5 g. (0.1 1 mole) of p-methoxybenzyl 4,6- dimethylpyrimidyl-2-thiolcarbonate in 55 ml. of dioxane, and the mixture was reacted under stirring at room temperature for 10 hours. After completion of the reaction, the reaction liquid was charged with 150 ml. of water and then extracted thrice with 200 ml. of ethyl acetate to remove unreacted thiolcarbonate. Thereafter, the aqueous phase was cooled to 0C., adjusted to pH 3 by addition of a 10 aqueous citric acid solution and then extracted once with 150 ml. of ethyl acetate and twice with ml. of ethyl acetate. Subsequently, the ethyl acetate phases were united together, washed twice with ml. of a 10 aqueous citric acid solution and twice with 100 ml. of water and dried over anhydrous sodium sulfate to obtain 24.3 g. of crystalline N-p-methoxybenzyloxycarbonylL-alanine in yield of 95.7 When recrystallized from an ethyl acetatepetroleum ether solvent, the product showed a melting point of 80 to 815C. and specific rotation l 01],, of -l2.2 (C 3. acetic acid).

For comparison, N-p-methoxybenzoxycarbonyl-L- alanine was synthesized by acylating L-alanine with known acylating agents. The results obtained were as set forth in Table 111. 

1. A THIOLCARBONATE REPRESENTED BY THE FORMULA,
 2. t-Butyl pyrimidyl-2-thiolcarbonate, or t-butyl 4-methyl- or 4,6-dimethyl-pyrimidyl-2-thiolcarbonate, in accordance with claim
 3. t-Amyl pyrimidyl-2-thiolcarbonate, or t-amyl 4-methyl- or 4, 6-dimethyl-pyrimidyl-2-thiolcarbonate, in accordance with claim
 4. Benzyl pyrimidyl-2-thiolcarbonate, or benzyl 4-methyl- or 4, 6-dimethyl-pyrimidyl-2-thiolcarbonate, in accordance with claim
 5. p-Methoxybenzyl pyrimidyl-2-thiolcarbonate, or p-methoxybenzyl 4-methyl- or 4,6-dimethyl-pyrimidyl-2-thiolcarbonate, in accordance with claim
 1. 6. 2,4-Dimethoxybenzyl pyrimidyl-2-thiolcarbonate, or 2,4-dimethoxybenzyl 4-methyl- or 4,6-dimethyl-pyrimidyl-2-thiolcarbonate, in accordance with claim
 1. 7. 2,4,6-Trimethoxybenzyl pyrimidyl-2-thiolcarbonate, or 2,4,6-trimethoxybenzyl-4-methyl- or 4,6-dimethyl-pyrimidyl-2-thiolcarbonate, iN accordance with claim
 1. 8. p-Nitrobenzyl pyrimidyl-2-thiolcarbonate, or p-nitrobenzyl 4-methyl- or 4,6-dimethyl-pyrimidyl-2-thiolcarbonate, in accordance with claim
 1. 9. p-Chlorobenzyl pyrimidyl-2-thiolcarbonate, or p-chlorobenzyl 4-methyl- or 4,6-dimethyl-pyrimidyl-2-thiolcarbonate, in accordance with claim
 1. 10. p-Bromobenzyl pyrimidyl-2-thiolcarbonate, or p-bromobenzyl 4-methyl- or 4,6-dimethyl-pyrimidyl-2-thiolcarbonate, in accordance with claim
 1. 11. Benzhydryl-pyrimidyl-2-thiolcarbonate, or benzhydryl 4-methyl- or 4,6-dimethyl-pyrimidyl-2-thiolcarbonate, in accordance with claim
 1. 